U.S. patent number 8,562,651 [Application Number 13/075,679] was granted by the patent office on 2013-10-22 for sacroiliac terminal anchor device and method.
This patent grant is currently assigned to Warsaw Orthopedic, Inc.. The grantee listed for this patent is Nicholas Benson, Newton Metcalf. Invention is credited to Nicholas Benson, Newton Metcalf.
United States Patent |
8,562,651 |
Metcalf , et al. |
October 22, 2013 |
Sacroiliac terminal anchor device and method
Abstract
A spinal stabilization apparatus and method according to which
an anchor element is engaged with a bone structure of a spinal
system. The anchor element defines a reservoir adapted to contain a
bone-growth promoting material and the reservoir is in fluid
communication with the bone structure via at least one aperture
defined in the anchor element. A rod-connecting element extend from
the anchor element and is adapted to extend outward from the bone
structure to engage at least a portion of a rod when the rod
extends within a vicinity of the spinal system and the bone
structure.
Inventors: |
Metcalf; Newton (Memphis,
TN), Benson; Nicholas (Cordova, TN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Metcalf; Newton
Benson; Nicholas |
Memphis
Cordova |
TN
TN |
US
US |
|
|
Assignee: |
Warsaw Orthopedic, Inc.
(Warsaw, IN)
|
Family
ID: |
46928225 |
Appl.
No.: |
13/075,679 |
Filed: |
March 30, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120253398 A1 |
Oct 4, 2012 |
|
Current U.S.
Class: |
606/264; 606/315;
606/266 |
Current CPC
Class: |
A61B
17/7055 (20130101); A61B 17/864 (20130101); A61B
17/7037 (20130101); A61B 17/869 (20130101) |
Current International
Class: |
A61B
17/70 (20060101) |
Field of
Search: |
;606/301-321 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Cunningham, Bryan W.; Lewis, Stephen, J.; Long, John; Dmitriev,
Anton E.; Linville, Douglas A,; Bridwell, Keith H; ,Biomechanical
evaluation of lumbosacral reconstruction techniques for
spondylolisthesis, SPINE0362-2436; 2002, vol. 27, No. 21, pp.
2321-2327 [7 page(s) (article)] (23 ref.). cited by
applicant.
|
Primary Examiner: Cumberledge; Jerry
Claims
What is claimed is:
1. A terminal anchor apparatus for stabilizing a spinal system, the
apparatus comprising: an anchor element adapted to be inserted into
a bone structure, the anchor element having a distal end and a
proximal end, the anchor element defining a reservoir adapted to
contain a bone-growth promoting material, the anchor element
defining at least one aperture therein such that the reservoir is
in fluid communication with the bone structure via the at least one
aperture, the anchor element having a longitudinal axis and a first
outer diameter extending radially outward from the longitudinal
axis; a post element extending from the proximal end of the anchor
element, the post element including a ball at a proximal end
thereof, wherein the post element is tiltable relative to the
longitudinal axis of the anchor element; and a rod-connecting
element operably engaged with the post element and having an inner
surface defining a cavity configured for movable disposal of the
ball such that the rod-connecting element is rotatable and tiltable
about the ball, the rod-connecting element comprising a rod
receiver positioned proximal of a proximal face of the anchor
element, the rod-connecting element being adapted to extend outward
from the bone structure, the rod-connecting element having a second
outer diameter, the rod-connecting element configured for operably
engaging at least a portion of a rod when the rod extends within a
vicinity of the spinal system and the bone structure; wherein the
first outer diameter of the anchor element is larger than the
second outer diameter of the rod-connecting element.
2. The apparatus of claim 1, wherein the rod receiver defines a
channel having an open top such that at least a portion of the rod
may be inserted into the channel by moving the rod in a first
sagittal plane.
3. The apparatus of claim 2, wherein the rod-receiver is rotatable
360 degrees in place relative to the anchor element to adjust and
fix the direction of extension of the at least a portion of the rod
in the first coronal plane.
4. The apparatus of claim 2, wherein the rod-receiver is tiltable
relative to the longitudinal axis of the anchor element.
5. The apparatus of claim 1, wherein the rod-connecting element
defines an aperture extending therethrough.
6. The apparatus of claim 1, wherein the anchor element comprises a
thread pattern disposed on an outer surface thereof.
7. The apparatus of claim 6, wherein the thread pattern comprises:
a first thread portion having a first pitch, the first thread
portion extending from the distal end of the anchor element to the
proximal end of the anchor element; and a second thread portion
disposed between adjacent threads of the first thread portion and
having the first pitch, the second thread portion extending from an
intermediate point disposed between the distal end of the anchor
element and the proximal end of the anchor element to the proximal
end of the anchor element; wherein the first thread portion results
in a distal thread density between the distal end of the anchor
element and the intermediate point, and wherein the combination of
the first thread portion and the second thread portion results in a
proximal thread density between the intermediate point and the
proximal end of the anchor element, the proximal thread density
being higher than the distal thread density.
8. A terminal anchor apparatus for stabilizing a spinal system, the
apparatus comprising: an anchor element adapted to be inserted into
a bone structure, the anchor element having a distal end and a
proximal end, the anchor element defining a reservoir adapted to
contain a bone-growth promoting material, the anchor element
defining at least one aperture therein such that the reservoir is
in fluid communication with the bone structure via the at least one
aperture, the anchor element having a longitudinal axis; a post
element extending from the proximal end of the anchor element, the
post element including a ball at a proximal end thereof; a
rod-connecting element having an inner surface defining a cavity
configured for movable disposal of the ball such that the
rod-connecting element is rotatable and tiltable about the ball,
the rod-connecting element being adapted to extend outward from the
bone structure, the rod-connecting element comprising a
rod-receiver positioned proximal of a proximal face of the anchor
element, a distal face of the rod-receiver being spaced apart from
a proximal face of the anchor element, the rod receiver defining a
channel having an open top such that at least a portion of the rod
may be inserted into the channel by moving the rod in a first
sagittal plane such that the rod-connecting element operably
engages at least a portion of a rod when the rod extends within a
vicinity of the spinal system and the bone structure; and a set
fastener configured to be operably engaged with the rod-receiver
such that the rod is secured in the channel by the cooperation of
the rod-receiver and the set fastener, and the anchor element
having a first outer diameter and the rod-connecting element having
a second outer diameter, wherein the first outer diameter of the
anchor element is larger than the second outer diameter of the
rod-connecting element.
9. The apparatus of claim 8, wherein the rod-receiver is rotatable
360 degrees in place relative to the anchor element to adjust and
fix the direction of extension of the at least a portion of the rod
in the first coronal plane.
10. The apparatus of claim 8, wherein the rod-receiver is tiltable
relative to the longitudinal axis of the anchor element.
11. The apparatus of claim 8, wherein the anchor element comprises
a thread pattern disposed on an outer surface thereof.
12. The apparatus of claim 11, wherein the thread pattern
comprises: a first thread portion having a first pitch, the first
thread portion extending from the distal end of the anchor element
to the proximal end of the anchor element; and a second thread
portion disposed between adjacent threads of the first thread
portion and having the first pitch, the second thread portion
extending from an intermediate point disposed between the distal
end of the anchor element and the proximal end of the anchor
element to the proximal end of the anchor element; wherein the
first thread portion results in a distal thread density between the
distal end of the anchor element and the intermediate point, and
wherein the combination of the first thread portion and the second
thread portion results in a proximal thread density between the
intermediate point and the proximal end of the anchor element, the
proximal thread density being higher than the distal thread
density.
Description
BACKGROUND
The present invention relates in general to spinal systems and in
particular to a spinal stabilization apparatus and method utilizing
sacroiliac constructs. To stabilize a spinal system including a
spinal column, the extent of displacement between adjacent
vertebrae in the spinal column may be reduced, and/or each pair of
adjacent vertebrae may be maintained in a desired spatial
relationship. In some cases, rods may be provided that are adapted
to extend within the vicinity of the spinal system (including, in
some instances, the sacrum and/or adjacent portions of the iliac
bones), and connectors may be provided that connect one or more of
the rods to one or more of the vertebrae in the spinal system
and/or to iliac structures on the pelvis. The rods and connectors
may assist in providing immobilization and/or stabilization to the
spinal system, and/or may serve as an adjunct to fusion of one or
more portions of the spinal system. An example of a system for
reducing displacement of a vertebra, in which a rod is employed, is
disclosed in U.S. Pat. No. 6,248,107 to Foley et al., the
disclosure of which is incorporated by reference.
For spinal stabilization systems that include one or more rods
connected to screws or other fasteners attaching the stabilization
system to the pelvis, the ability to securely fasten at least a
portion of the system to one or more portions of the sacroiliac
region may be desired and/or required in order to more prevent the
construct from pulling out of or fracturing a pelvic or sacral
structure, among other desires and/or requirements. In addition,
the ability to utilize bone graft or other bone-growth promotion
agents to securely fasten at least a portion of the system to one
or more portions of the sacroiliac region may also be desired
and/or required. For example, a bone graft "cage" assembly may be
ideally suited for anchoring a sacroiliac terminal structure in the
bony structures of the ala.
As used herein, it is understood that the term "coronal plane"
includes any plane of section in the anatomical position that
generally passes vertically through the human body and is generally
perpendicular to both the median (or sagittal) plane and the
horizontal (or axial or transverse) plane, generally dividing the
human body into anterior and posterior sections, and further
includes any plane of section in the anatomical position that
generally passes vertically through the human body, is generally
perpendicular to the horizontal (or axial or transverse) plane, and
is generally angularly oriented from the median (or sagittal) plane
at an angle of orientation ranging from greater than zero degrees
up to and including ninety degrees.
Furthermore, as used herein, it is understood that the term
"sagittal plane" includes any plane of section in the anatomical
position that generally passes vertically through the human body in
the prone position and is generally perpendicular to both the
coronal plane and the horizontal (or axial or transverse) plane,
generally dividing the human body into left and right sections, and
further includes any plane of section in the anatomical position
that generally passes vertically through the human body in the
prone position, is generally perpendicular to the horizontal (or
axial or transverse) plane, and is generally angularly oriented
from the coronal plane at an angle of orientation ranging from
greater than zero degrees up to and including ninety degrees.
SUMMARY OF THE INVENTION
An apparatus for stabilizing a spinal system is provided that
includes a terminal anchor device adapted to be coupled to a bone
structure (including, but not limited to the sacrum and ilia). In
one embodiment, the terminal anchor apparatus comprises an anchor
element adapted to be inserted into a bone structure. The anchor
element defines a reservoir adapted to contain a bone-growth
promoting material and at least one aperture therein such that the
reservoir is in fluid communication with the bone structure. The
terminal anchor apparatus also comprises a rod-connecting element
extending from a proximal end of the anchor element and adapted to
extend outward from the bone structure such that the rod-connecting
element is configured for operably engaging at least a portion of a
rod when the rod extends within a vicinity of the spinal system and
the bone structure.
A method of stabilizing a spinal system is also provided, the
method comprising defining a hole in a sacroiliac bone structure
and providing a sacroiliac terminal anchor assembly adapted for
insertion into the bone structure. As noted herein, the terminal
anchor assembly may comprise an anchor element adapted to be
inserted into a bone structure, wherein the anchor element defines
a reservoir adapted to contain a bone-growth promoting material and
at least one aperture therein such that the reservoir is in fluid
communication with the bone structure. The anchor assembly also
comprises a rod-connecting element extending from a proximal end of
the anchor element and adapted to extend outward from the bone
structure such that the rod-connecting element is configured for
operably engaging at least a portion of a rod when the rod extends
within a vicinity of the spinal system and the bone structure. The
method further comprises packing the reservoir of the anchor
element with the bone-growth promoting material, placing the
sacroiliac terminal anchor assembly in the hole defined in the
sacroiliac bone, and inserting at least a portion of a rod into a
channel defined in the rod-connecting element by moving the rod in
a first sagittal plane, such that the rod-connecting element
operably engages at least a portion of a rod when the rod extends
within a vicinity of the spinal system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a terminal anchor apparatus
according to one embodiment.
FIG. 2 is a perspective view of a terminal anchor apparatus
according to one embodiment wherein the anchor element comprises a
dual-thread pattern.
FIG. 3a is a partial perspective view of a terminal anchor
apparatus according to one embodiment wherein the rod-connecting
element comprises a multi-axial head.
FIG. 3b is a partial perspective view of the terminal anchor
apparatus shown in FIG. 3a wherein the rod-connecting element is
shown angulated relative to the anchor element.
FIG. 4a is a partial perspective view of a terminal anchor
apparatus according to one embodiment wherein the rod-connecting
element comprises a post.
FIG. 4b is a partial perspective view of a terminal anchor
apparatus according to one embodiment wherein the rod-connecting
element comprises an angulating post.
FIG. 5 is a cross-sectional view of a terminal anchor apparatus
according to one embodiment.
FIG. 6a is a partial perspective view of a terminal anchor
apparatus according to one embodiment wherein the rod-connecting
element comprises a post defining a lateral channel for receiving a
connector element.
FIG. 6b is a partial perspective view of a terminal anchor
apparatus according to one embodiment wherein the rod-connecting
element comprises a fixed-angle post defining a lateral channel for
receiving a connector element.
FIG. 7 is a perspective view of an apparatus for stabilizing a
spinal system comprising a terminal anchor apparatus according to
one embodiment, wherein the terminal anchor apparatus is engaged
with a portion of the iliac crest.
FIG. 8 is a perspective view of an apparatus for stabilizing a
spinal system comprising a terminal anchor apparatus according to
one embodiment, wherein the terminal anchor apparatus is engaged
with a portion of the ilia.
DETAILED DESCRIPTION
Referring to FIGS. 7 and 8, a spinal system is generally referred
to by the reference numeral 1 and includes vertebrae 2, 4, 6, 8,
sacrum 3, and ilia 5,7. It is understood that the spinal system 11
includes a human spinal column composed of various types of
vertebrae, of which the vertebrae 2, 4, 6 and 8 are a part, and
ligaments and/or other natural and/or artificial structures
connected to and/or extending between one or more of the vertebrae.
Also shown is the sacrum 3, and ilia 5,7 making up the sacroiliac
bone structure in the vicinity of the spinal system 1. Rods R
extend within the vicinity of the spinal system 1 and the
sacroiliac bone structure in a spaced relation. Fasteners, in the
form of pedicle screws P1-P8, are threadably engaged with and
extend from the pedicles on both sides of vertebrae 2, 4, 6 and 8,
respectively. In addition, a fastener, in the form of a terminal
anchor apparatus 10 is threadably engaged with and extend from the
ilia 5,7 of the sacroiliac bone structures.
As shown generally in FIGS. 7 and 8, pedicle screws P1, P2, P3, P4,
P5, P6, P7 and P8 are coupled to the rod R by set screws engaged
with saddles, screw "tulips" and/or other connecting elements.
Likewise, connector 50 may be engaged with the terminal anchor
apparatus 10, and may be coupled to the rod R, thereby connecting
the terminal anchor apparatus 10 to the rod R. In some embodiments,
the connector 50 is coupled to the rod 18 via a second fastener 52
(which may include, but is not limited to, a set screw as shown
generally in FIGS. 6A and 6B). In other embodiments, the terminal
anchor apparatus 10 may comprise a rotatable and/or angulating
rod-connecting element 30 (see FIGS. 1 and 2, for example) coupled
to a proximal end 22 of the anchor element 20. In some such
embodiments, the rod-connecting element 30 may be configured for
directly receiving the rod R without the need for a separate
connector 50.
Referring to FIG. 1, one embodiment of a terminal anchor apparatus
10 is shown for stabilizing a spinal system 1. The terminal anchor
apparatus 10 comprises an anchor element 20 adapted to be inserted
into a bone structure (such as the ilia 5,7, sacrum 3) as shown
generally in FIGS. 7 and 8). In some embodiments, the terminal
anchor apparatus 10 may also be implanted into and/or across the
sacroiliac (SI) joint. The anchor element 20 has a distal end 21
and a proximal end 22 and extends along a longitudinal axis L.
Anchor element 20 is shown herein as generally circular or ovoid in
cross-section generally orthogonal to longitudinal axis L. The
anchor element 20 may be defined by a first outer diameter wherein,
in some embodiment, the first diameter of the anchor element 20,
may be greater than a corresponding outer diameter of
rod-connecting element 30 described further herein. As shown
generally in FIG. 5, the anchor element 20 defines a reservoir 26
adapted to contain a bone-growth promoting material. For example,
the anchor element 20 may be formed from the components of an
inter-vertebral implant cage defining the reservoir 26 adapted to
contain bone-growth promoting material that may include, but is not
limited to: allograft, autograft (including native bone and/or bone
harvested from the iliac bone structures) xenograft, and/or various
types of bone morphogenetic protein (BMP). As shown in FIG. 1, the
anchor element 20 defines at least one aperture 23 therein such
that the reservoir 26 is in fluid communication with the bone
structure via the at least one aperture 23 (thereby allowing the
bone-growth promoting material to come into contact with the bone
structures of the ilia 5, 7 or sacrum 3 where the terminal anchor
apparatus 10 may be implanted by a surgeon). The anchor element 20
may be formed from a variety of inert and/or biocompatible
engineering materials including, but not limited to: polymers,
polymer blends, metals, alloys and/or combinations thereof.
As shown in FIGS. 1 and 2, the anchor element 20 may define a
plurality of apertures 23 having a variety of diameters optimized
for the type of bone structure 3, 5, 7 into which the terminal
anchor apparatus 10 is placed and/or for the type of bone-growth
promoting material placed into the reservoir 26 of the anchor
element 20. For example, one aperture 23 diameter and/or
configuration may be suitable for fluid communication with cortical
bone that may be present on the surface of the bone structure 3, 5,
7 while another aperture 23 diameter and/or configuration may be
suitable for fluid communication with trabecular and/or cancellous
bone that may be present in the interior of the bone structure 3,
5, 7. As shown generally in FIGS. 1 and 2, the apertures 23 may
comprise a series of substantially-round and/or ovoid holes defined
in the anchor element 20. The apertures 23 may be defined in a
single row and/or multiple rows between adjacent threads 24 of a
thread pattern that may be disposed on an outer surface of the
anchor element 20. The apertures 23 may also be placed, sized,
and/or shaped to suit the type of bone-growth promoting material
placed into the reservoir 26. For example, larger apertures 23 may
allow for better communication (and more rapid bone growth) between
the reservoir 26 and the surrounding bone structure 3, 5, 7. Such
larger apertures 23 may also be adequate to contain larger pieces
of allograft, autograft and/or other bone components. However,
smaller apertures 23 in a denser concentration may preserve fluid
communication between the reservoir 26 and the surrounding bone
structure 3, 5, 7 while still allowing for the containment of
smaller particles of bone-growth promoting material 70 (see FIG. 5,
for example). As shown in FIG. 5, the anchor element 20 may define
an additional plurality of apertures 23a, 23b, 23c having a variety
of diameters in the proximal end 22 and the distal end 21 of the
anchor element 20. The apertures 23a, 23b, 23c may be useful in
establishing communication between the reservoir 26 and the
surrounding bone structure. Furthermore, the various proximal
and/or distal apertures 23a, 23b, 23c may also provide openings
through which a clinician may pack bone-growth promoting material
70 into the reservoir 26 prior to the implantation of the terminal
anchor apparatus 10.
As shown in FIGS. 1 and 2, the anchor element 20 may comprise a
thread pattern 24 disposed on an outer surface thereof. The threads
24 may be configured to interact with a tapped hole defined in the
bone structure 3, 5, 7 by a surgeon in preparation for the
implantation of the terminal anchor apparatus 10. The threads 24
may comprise compressive threads suitable for compressing the bone
into which the anchor element 20 may be threaded. Furthermore, it
should be understood that the threads 24 may comprise a variety of
cross-sectional shapes, pitches, thread densities, and whose design
may be optimized for various types of bone applications. For
example, in some such embodiments, the thread pattern 24 may
comprise a dual-thread arrangement wherein a proximal end of the
anchor element 20 has a thread density greater than a distal end of
the anchor element 20. This configuration may allow the anchor
element 20 to more effectively grip the various types of bone that
it may encounter upon implantation into the bone structure 3, 5, 7.
For example, the surface bone of the bone structure 3, 5, 7 may
comprise comparatively-dense cortical bone that may require a
similarly-dense thread pattern to adequately grip and/or compress
the bone. Furthermore, interior bone of the bone structure 3, 5, 7
may comprise less-dense trabecular and/or cancellous bone that may
require a relatively less-dense thread pattern to grip and/or
compress the bone. Therefore, in some such embodiments as shown in
FIG. 2, the thread pattern 24 comprises a first thread portion 24a
having a first pitch, the first thread portion extending from the
distal end 21 of the anchor element 20 to the proximal end 22 of
the anchor element 20. The thread portion 20 may also comprise a
second thread portion 24b disposed between adjacent threads of the
first thread portion 24a and having the first pitch. In order to
increase the overall thread density at a proximal portion of the
anchor element 20, the second thread portion 24b may extend from an
intermediate point 25 disposed between the distal end 21 of the
anchor element 20 and the proximal end 22 of the anchor element 20
to the proximal end 22 of the anchor element 20. In such
embodiments, the first thread portion 24a results in a distal
thread density between the distal end 21 of the anchor element 20
and the intermediate point 25, and the combination of the first
thread portion 24a and the second thread portion 24b results in a
proximal thread density between the intermediate point 25 and the
proximal end 22 of the anchor element 20, wherein the proximal
thread density is higher than the distal thread density.
The terminal anchor apparatus 10 also comprises a rod-connecting
element 30 extending from the proximal end 22 of the anchor element
20. As shown generally in FIGS. 7 and 8, the rod-connecting element
30 is adapted to extend outward from the bone structure (including
but not limited to the ilia 5,7 and/or sacrum 3). The
rod-connecting element 30 may comprise a variety of different inert
and/or biocompatible materials suitable for connecting to and/or
receiving a spinal rod R. For example, the rod-connecting element
30 may incorporate engineering materials including, but not limited
to: stainless steel, titanium, cobalt-chrome, polymer and/or
combinations thereof. The rod-connecting element 30 has a second
outer diameter (extending radially outward from longitudinal axis
L) and is configured for operably engaging at least a portion of a
rod R when the rod R extends within a vicinity of the spinal system
1 and the bone structure (3, 5 and 7, for example, as shown in
FIGS. 7 and 8).
As shown herein (see FIG. 5, for example), the first outer diameter
of the anchor element 20 may, in some embodiments, be larger than
the second outer diameter of the rod-connecting element 30 such
that the anchor element 20 has adequate capacity to contain
bone-growth promoting material suitable for initiating bone growth
and integration of the anchor device 20 into the bone structure 3,
5, 7 after implantation of the terminal anchor apparatus 10. In
this way, the terminal anchor apparatus 10 described herein may be
superior to conventional iliac screws for securely anchoring a
sacroiliac surgical construct by allowing for the use of
bone-growth promoting material 70 within the insertion site of the
anchor element 20 of the terminal anchor apparatus 10.
It should be understood that the rod-connecting element 30 may be
operably engaged with the anchor element 20 via a number of
different techniques. For example, in some embodiments, the at
least a portion of the rod-connecting element 30 (such as the post
35) may be integrally formed with the anchor element 20. In other
embodiments, such as that shown generally in FIG. 5, the post 35 of
the rod-connecting element 30 may be threaded and/or otherwise
inserted into a complementary aperture formed in the proximal end
22 of the anchor element. In such embodiments, the post 35 may
comprise a plurality of threads 35a suitable for receiving and/or
operably engaging a nut 38 that may act to secure the post 35 to
the anchor element 20. In some embodiments, a washer 39 may be
inserted between the nut 39 and an interior surface of the anchor
element 20 in order to more securely fasten the rod-connecting
element 30 with the anchor element 20. In some embodiments, the
washer 39 may be integrally formed with the post 35 to form a
flange that may be attached via adhesive and/or mechanical
fasteners to the anchor element 20. In some embodiments, the post
35 may also comprise an upper flange 39a that may cooperate with
the nut 38 and washer 39 to grip the proximal end 22 of the anchor
element 20 therebetween.
As shown herein (see FIG. 1, for example) the rod-connecting
element 30 may comprise a rod-receiver 31 (including but not
limited to a "tulip"-style fixed and/or multi-axial pedicle screw
head found in the CD Horizon Legacy.RTM. or the CD Horizon
Solera.RTM. lines of spinal instrumentation developed by Medtronic
Spinal and Biologics of Memphis, Tenn.). The rod-receiver 31 may
define a channel 32 having an open top such that at least a portion
of a spinal rod R may be inserted into the channel by moving the
rod R in a first sagittal plane when the patient is oriented
generally in a prone surgical position to allow surgical access to
the spinal system 1. As shown in FIGS. 1 and 2, the terminal anchor
apparatus 10 may further comprise a set fastener 40 configured to
be operably engaged with the rod-receiver 31 such that the rod R is
secured in the channel 32 by the cooperation of the rod-receiver 31
and the set fastener 40.
As shown in FIG. 3A, the rod receiver 31 may be rotatable 360
degrees in place relative to the anchor element 20 to allow for
complete angular adjustability of the rod-connecting element 30
relative to the anchor element 20 (which may be substantially fixed
in the bone structure). Such embodiments may allow for rotation
(RA) as shown in FIGS. 3A and 3B about the longitudinal axis L of
the terminal anchor apparatus 10. While the rotation (RA) is shown
as a counterclockwise rotation in FIGS. 3A and 3B, it should be
understood that the rod receiver 31 may be rotatable 360 degrees in
place in both clockwise and counterclockwise directions in place
relative to the anchor element 20 to fully adjust and, in some
embodiments, fix the direction of extension of at least a portion
of the rod R in a first coronal plane.
In other embodiments, as shown in FIG. 3B, the rod-receiver 31 may
be tiltable relative to the longitudinal axis L of the anchor
element 20 in order to allow for a wider range of positions to
account for differences in morphology of the bone structure 3, 5, 7
and/or to better allow for easier engagement of the rod R between
the terminal anchor apparatus 10 and any combination of pedicle
screws P1-P8 (see FIG. 7, for example) that may be used to fully
instrument a spinal system 1 as part of a surgical procedure. As
noted herein, the rod-receiver 31 may comprise a multi-axial screw
(MAS) "tulip"-style screw head found in the CD Horizon Legacy.RTM.
or the CD Horizon Solera.RTM. lines of spinal instrumentation
developed by Medtronic Spinal and Biologics of Memphis, Tenn. As
shown in FIG. 3B, the rod-receiver 31 may thereby be tilted to a
tilt axis T that is separated from the longitudinal axis L of the
terminal anchor apparatus 10 by angle A.
As shown in FIG. 5, the rotatable and/or tiltable rod-receiver 31
embodiments of the terminal anchor apparatus 10 may comprise a ball
34 engaged with a post 35 extending from the proximal end 22 of the
anchor element 20. The ball 34 may be inserted into a collar 33
formed at a distal end of the rod-receiver 31 such that the collar
33 is rotatable and/or tiltable about the ball 34. Furthermore, the
rod-receiver 31 selectively fixed at an angle A and at a rotational
position RA relative to the ball 34 (and the anchor element 20) by
inserting the rod R into the channel 32 and securing the rod in the
channel 32 via the engagement of a set screw 40 with a proximal end
of the rod-receiver 31. The set screw 40 may therefore be brought
to bear against a substantially flat upper surface of the ball 34
(as shown in the exemplary cross-section of FIG. 5) by the set
screw 40 in order to fix the rod-receiver 31 at an angle A and at a
rotational position RA relative to the ball 34 (and the anchor
element 20).
Referring to FIG. 4A, in some embodiments, the terminal anchor
apparatus 10 may comprise a rod-connecting element 30 embodied as a
post 35 adapted to operably engage a connector device (not shown)
for operably engaging at least a portion of the rod R. For example,
the post 35 may serve as an attachment point for a variety of
angulating and/or fixed connector devices including, but not
limited to the TSRH-3D.RTM. small, medium and large connectors and
TSRH-3D.RTM. 90-degree offset connectors developed by Medtronic
Spinal and Biologics of Memphis, Tenn. In such embodiments, the
post 35 may comprise a drive aperture 36 (including, not limited
to: a female Torx.RTM. interface, a female hex drive interface)
that may allow a surgeon to drive the terminal anchor apparatus 10
into a hole defined in the bone structure 3, 5, 7 by rotating the
post 35 and the anchor element 20.
In other embodiments, as shown in FIG. 4B, the terminal anchor
apparatus 10 may also comprise a post 35 that is pivotable or
tiltable relative to the longitudinal axis L of the anchor element
20. For example, such embodiments may comprise a post 35 having a
pivot 37 attached to a proximal end thereof, and a pivotable post
element 35a operably engaged with the pivot 37 such that the
pivotable post element 35a may be pivotable relative to the
longitudinal axis L of the anchor element. Such pivotable
embodiments may be compatible with a variety of components and
instruments available from the TSRH-3D.RTM. PLUS MPA.TM.
multi-planar screw system developed by Medtronic Spinal and
Biologics of Memphis, Tenn.
Referring now to FIGS. 6A and 6B, the terminal anchor apparatus
may, in some embodiments also comprise a rod-connecting element 30
(such as the post 35) defining an aperture 32 extending
therethrough. For example, the post 35 may comprise a rod-receiver
31 wherein the rod-receiver 31 has a closed top defining the
aperture 32. A set screw 40 may be engaged with a threaded aperture
defined in a top portion of the rod-receiver 31 in order to secure
a rod-portion of a connector element 50 therein. The connector
element 50 may therefore allow for lateral positioning of a spinal
rod R (see FIGS. 7 and 8, for example) relative to the terminal
anchor element 10. The connector element 50 may comprise a variety
of lateral ilio-sacral connector elements having rod portions that
are compatible with the rod-connecting element 30 of the terminal
anchor element 10. As shown in FIG. 6A, the connector element 50
may define a rod-receiver aperture 51 sized to receive the spinal
rod R. The connector element 50 may also comprise a set screw 52
configured to secure the spinal rod R in the rod-receiver aperture
51 in order to complete an ilio-sacral terminal construct such as
that shown generally in FIG. 7 and/or FIG. 8. As shown in FIG. 6B,
in some such embodiments, the rod-connecting element 30 may
comprise a post 35 and rod-receiver 31 that are tilted at an angle
A relative to the longitudinal axis L of the terminal anchor
element 10. Such embodiments may be useful in some surgical
constructs wherein the terminal anchor element 10 is inserted into
a bony structure 3, 5, 7 that is displaced at an angle relative to
an axis defined by the spinal system 1.
Various methods for stabilizing a spinal system 1 are also provided
herein, wherein the method first comprises defining a hole in a
sacroiliac bone structure (including, but not limited to the ilia
5,7, sacrum 3, and/or the sacroiliac (SI) joint). The hole may be
defined by a surgeon using a variety of techniques and instruments,
including but not limited to surgical taps, reamers, drills, bits,
and/or other devices. In some embodiments, the method may comprise
defining the hole in the sacroiliac bone structure 3, 5, 7 using a
tap having threads matching a thread pattern 24 defined on an outer
surface of a terminal anchor element 10 such as that shown
generally in FIG. 2. For example, the defining step may comprise
defining a female thread pattern in the hole in the sacroiliac bone
structure 3, 5, 7, and the providing step described further herein,
may further comprise providing a male thread pattern 24 disposed on
an outer surface of the anchor element 20 wherein the male thread
pattern 24 is configured for engaging the female thread pattern to
secure the anchor element 20 in the hole. As described herein, the
threads 24 may be formed to compress bone material so as to more
securely fasten the anchor element 20 within the bone structure 3,
5, 7.
In method embodiments, wherein the anchor element 20 is provided
with a male thread pattern, the pattern may comprise (see FIG. 2) a
first thread portion 24a having a first pitch, the first thread
portion 24a extending from the distal end 21 of the anchor element
20 to the proximal end 22 of the anchor element 20. The pattern may
further comprise a second thread portion 24b disposed between
adjacent threads of the first thread portion 24a and also having
the first pitch. The second thread portion 24b extends from an
intermediate point 25 disposed between the distal end 22 of the
anchor element 20 and the proximal end 21 of the anchor element 20
to the proximal end 22 of the anchor element 20. In such
embodiments, the first thread portion 24a results in a distal
thread density between the distal end 21 of the anchor element 20
and the intermediate point 20. Furthermore, the combination of the
first thread portion 24a and the second thread portion 24b results
in a proximal thread density between the intermediate point 25 and
the proximal end 22 of the anchor element 20, wherein the proximal
thread density is higher than the distal thread density.
Various method embodiments comprise providing a sacroiliac terminal
anchor assembly (such as the various embodiments of the terminal
anchor element 10, described herein). As noted herein with respect
to FIGS. 1-8, the sacroiliac terminal anchor assembly may comprise
an anchor element 20 having a distal end 21, a proximal end 22 and
a longitudinal axis L. Furthermore, the anchor element 20 may
define a reservoir 26 therein (see FIG. 5) adapted to contain a
bone-growth promoting material 70. The anchor element 20 also
defines at least one aperture 23 (see also apertures 23a, 23b, 23c
shown in FIG. 5) therein such that the reservoir 26 is in fluid
communication with an exterior of the anchor element 20. The
sacroiliac terminal anchor assembly may further comprise a variety
of different rod-connecting elements 30 as described in detail
herein. The rod-connecting element 30 extends from the proximal end
22 of the anchor element 20 and may be adapted to extend outward
from the bone structure 3, 5, 7 when the anchor element 20 is
inserted into the hole defined in the bone structure 3, 5, 7.
Furthermore, the rod-connecting element 30 comprises at least one
type of rod-receiver 31 (including, but not limited to a post 35 as
shown in FIG. 4A suitable for interface with a connector that may,
in turn, be configured for receiving a spinal rod R). In other
embodiments, as shown in FIGS. 1-2, 3A and 3B, the rod-receiver 31
may define a channel 32 having an open top configured for receiving
the rod R therein (see FIG. 1, for example).
The method embodiments further comprise packing the reservoir 26 of
the anchor element 20 with the bone-growth promoting material 70
(see FIG. 5, for example). The packing step may comprise packing
bone-growth promoting material 70 through apertures 23a, 23b
located on a proximal end 22 of the anchor element 20 and/or
packing bone-growth material 70 through aperture 23c located on a
distal end 21 of the anchor element. As described herein, the
bone-growth promoting material 70 may include, but is not limited
to: allograft, autograft, xenograft, and/or bone morphogenetic
protein (BMP).
The method embodiments further comprise placing the sacroiliac
terminal anchor assembly 10 in the hole defined in the sacroiliac
bone structure 3, 5 and/or 7 (see FIGS. 7 and 8, for example) such
that the anchor element 20 is disposed substantially within the
hole. Thus, the bone-growth promoting material 70 may be in fluid
communication with the sacroiliac bone structure 3, 5, 7 via the at
least one aperture 23 defined in the anchor element 20.
Furthermore, as shown generally in FIGS. 7 and 8, the
rod-connecting element 30 extends substantially out of the hole
such that the method may further comprise inserting at least a
portion of a rod R into the channel 32 defined in the
rod-connecting element 30 by moving the rod R in a first sagittal
plane, such that the rod-connecting element 30 operably engages at
least a portion of the rod R when the rod R extends within a
vicinity of the spinal system 1.
As shown in FIGS. 3A and 3B, the rod connecting element 30 (and/or
a rod-receiver 31 thereof) may be rotatable (see rotational
movement denoted by RA) about the longitudinal axis L of the anchor
element 20. In such embodiments, the method may further comprise
selectively adjusting the direction of extension of at least a
portion of the rod R in a first coronal plane by rotating the
rod-connecting element 30 relative to the anchor element 20. Such
method embodiments may further comprise locking the direction of
extension of the at least a portion of the rod R. For example, the
locking step may be accomplished in some embodiments by engaging a
set fastener 40 (see FIG. 5) with the rod-receiver 31 in order to
"lock down" the rod R against a flat top portion of the ball 34
engaged with a proximal end of the post 35.
It is understood that any foregoing spatial references, such as
"top," "bottom." "upper," "lower," "above," "below," "between,"
"vertical," "angular," "up," "down," "right," "left," etc., are for
the purpose of illustration only and do not limit the specific
orientation or location of the structure described above.
Moreover, it is understood that any of the terminal anchor
apparatus 10 embodiments described herein may be used in the iliac
bones 5, 7, the sacrum 3, the sacroiliac (SI) joint, in any iliac
bone structure and/or in any location, and with any type of
vertebra and/or any natural and/or artificial structure extending
to or from the vertebra, within the spinal system 1. It is further
understood that the cross-sections of the rods R extending within
the vicinity of the spinal system 1 may be varied, and that the
corresponding cross-sections of the channels 32 of the
rod-connecting element 30 into which the rods R may be placed may
also be correspondingly varied.
Also, it is understood that each of the above-described embodiments
may be combined in whole or in part with one or more of the other
above-described embodiments. It is further understood that each of
the above-described embodiments may be combined in whole or in part
with other components, devices, systems, methods and/or surgical
techniques known to those skilled in the art to provide spinal
stabilization.
Although exemplary embodiments of this invention have been
described in detail above, those skilled in the art will readily
appreciate that many other modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents, but also equivalent structures.
* * * * *